Herbicides



UNITED STATES PATENT OFFICE HERBICIDES Arthur H. Schlesinger and David T. Mowry, D

ton, Ohio, assignors to Monsanto Che Company, St. Louis, Mo., a corporation of Delaware No Drawing. Application September 26, 1950, Serial No. 186,921

Claims. (CI. 71-25) 1 2 The present invention relates to herbicides and Another group comprises compounds having deals more particularly with methods for the genthe general formula eral destruction of undesired plants. ON

A number of herbicides are known, a variety of organic and inorganic compounds having been 5 Y OH=(]JCN suggested in the prior art for use as plant-killers. in Which Y S lec d 'Om the Class 00h tin Among the disadvantages of known herbicides of O-a1ky d y radicals of t0 3 may be mentioned corrosive effect on equipment, C bo at This eleSS of Compounds 13 chemical reactivity with other components cusprepared y reaching an elkyl y 0? tomarily employed in agricultural sprays or powformate with malononitrile in the presence of ders, instability when exposed for long periods of a dehydrating agent d includes, f e p time to ordinary atmospheric conditions, and soil methOXymethyleneihalolionitrile, ethoxymethylinstability, e. g., chemical reactivity with soil enemaloneniiilile, bHtOXYmethylenemalononitrile, components and susceptibility to decomposition xyl xym t yl m lo i il o yl ym hby soil micro-organisms, which results in loss of 15 ylenemalononitrile, phenoxymethylenemalonothe active material. Thus, a herbicide possessing i le, .8I1&Dhi?hy10Xymethy1eI1emaiononitrile,

a free carboxy group may be substantially det activated in highly alkaline soil by reaction with Still another r p of compounds wh h r basic, salt-forming materials in such soils. Conul r the pr t purp s ha th ra versely, a herbicide having reactive basic subformula stituents may be deactivated by reaction with 0N acid constituents of acidic soils.

Now We have found that highly stable, noncorrosive herbicidal compositions are obtained by employing as the active ingredient a compound selected from the class consisting of malononitrile and the derivatives of malononitrile which have the general formula ZCH=( JON in which Z is selected from the class consisting of the furyl and thienyl radicals and derivatives thereof in which at least one nuclear hydrogen has been substituted by an alkyl radical of from 1 to 4 carbon atoms. This class of compounds includes furalmalononitrile and thenalmalononi- R ON 4 trile.

The present malononitriles are effective herbicides over wide ranges of concentrations. The in which R and R are selected from the class effectiveness maybe measured y determining e consisting of hydrogen, alkyl, aryl, cycloalkyl, inhibition of root growth as compared to similar O.alkyl, O-cycloa1kyl, and -O.aryl radicals untreated plants. The general usefulness of a of from 1 to 8 carbon atoms, the furyl radical, and h rbicid m y be m r y par n h th thienyl di l concentrations of a herbicide required to produce Derivatives of malononitrile which we have a certain inhibition on a bread-leafed plant With found t possess Very good h i l ti may the concentrations of a herbicide required to probe classed as follows; 40 duce the same inhibition on a narrow-leafed Compounds having t general formula, plant. For evaluation in many laboratories the cucumber has been adopted as a typical broad- ON leafed dicotyledonous plant for technical reasons,

c and wheat has been used as a standard narrowleafed monocotyledonous plant. The general in which X is selected from the class consisting of technique f evamation of herbicides by growing yd a y eyeleelkyl, y and alkaryl seedlings in petri dishes has been described by radicals of from 1 to 8 carbon atoms. This class Thompson Swanson and Norman, Botanical of compounds is easily prepared by reacting an zette, 107, 476-507 (1946). aldehyde with malononitrile and includes, for ex- The present i ti i iu t ted, b t not ample, ethylidenemalononitrile, l-phenylethyllimited, by t following m idenemalononitrile, benzylidenemalononitrile, cy-

c10hexylidenemalononitrile, isopropylidenemal- Example I ononitrile, 1 methylbutylidenemalononitrile, Herbicidal activity of the nitriles listed in the a methylcuminylideneinalononitrile, diphenyltable below was determined by germination of malononitrile, etc. cucumber seeds for 4 days at a temperature of 76 F. in the presence of aqueous suspensions of each of the indicated chemicals at concentration of 100 p. p. m. Seventy-five seeds were used for each test. The results are expressed as per cent length of the primary roots in the presence of the chemical compared with the length of the primary roots of controls which had been germinated in water. The activity of two standard herbicides as obtained by the same test are included for comparison.

Percent Compound Tested fgggig Per Million Malononltrilc 3 Furalmalononitrile... 2 Thenalmalononitrile 3 Ethoxymcthylenemalononi l Benzylidenemalononitrile 13 1-Phony]ethylidcnemalononlt l9 2,4-Dicl1lorophenoxyacetic acid. 6 Isopropyl carbanilate 14 The herbicidal efiiciency of malononitrile and the present derivatives thereof, is remarkable, because as shown in the table given below nitriles do notgenerally possess great herbicidal efficiency. ,When tested as described above, aqueous suspensions of a random group of nitriles were found to have the following effects:

Example II The present malononitrile compounds were tested with both cucumber and wheat seeds and the percentage of growth inhibition measured for various concentrations. The concentration of each compound which permitted'20 per cent of normal growth (80 per cent inhibition) was determined'for seeds of cucumber and wheat, re- I spectively. The following results, expressed as parts per million of the herbicide, were obtained:

Cucumber Wheat Ratio Malononitrile l8 17 l Furalmalononitrilc. 23 59 2. Thenalmalononitrile 16 16 l Ethoxyrncthylenemalononit 35 80 2. 3 Benzylidencmalononitrile. 35 100 3 1-Phenylcthylidenemalononitrile 14 28 2 I P. p. m. for 50% growth used.

The nitriles are preferably applied by-spraying aqueous suspensions of the same, this method affording an easy and inexpensive way of destroying plant growth. However, the present nitriles are likewise efiective when applied as tion to the undesirable plants, or they may be employed to prevent the plant growth by application to soils. When employed to prevent plant growth, for example in parking areas, highway abutments, railway yards, etc., they may be applied either as an aqueous spray or dust or they may be admixed with customarily employed temporary surfacing materials, e. g., oils, cinders, etc.

The present invention thus provides a generally useful method of preventing and destroying undesirable plant growth.

Only small amounts of the present herbicidal materials need be employed. For general utility, concentrations of from, say, 0.1 part to 20 parts of thenitrileper hundred parts by weight of the carrier may be employed, and in this manner an acre of land may be freed of plants by application of only a few pounds of one of the present herbicides.

What we claim is:

l. The method of destroying undesirable plants which comprises applying to said plants a toxic quantity of a herbicidal composition including, as the active ingredient, a compound selected from the class consisting of malononitrile and derivatives of malononitrile, said derivatives having the formula R CN R( J=( lON in which R is selected from the class consisting of the cyclopropyl, the furyl and the thienyl radicals and R is selected from the class consisting of hydrogen and the methyl radical.

2. The method of destroying undesirable plants which comprises applying to said plants a herbicidal composition including l-cyclopropylethylidenemalononitrile as the active ingredient.

3. The method of destroying undesired plants which comprises applying to said plants a toxic quantity of a herbicidal composition including malononitrile as the active ingredient.

4. The method of destroying undesired plants which comprises applying to said plants a toxic quantity of a herbicidal composition including furalmalononitrile as the active ingredient.

5. The method of destroying undesired plants which comprises applying to said plants a toxic quantity of a herbicidal composition including thenalmalononitrile asthe active ingredient.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Sexton June 7, 1949 Number 

1. THE METHOD OF DESTROYING UNDESIRABLE PLANTS WHICH COMPRISES APPLYING TO SAID PLANTS A TOXIC QUANTITY OF HERBICIDAL COMPOSITION INCLUDING, AS THE ACTIVE INGREDIENT, A COMPOUND SELECTED FROM THE CLASS CONSISTING OF MALONONITRILE AND DERIVATIVES OF MALONONITRILE, SAID DERIVATIVES HAVING THE FORMULA 